Hydraulic Jar Firing Isolation Device

ABSTRACT

A jar device is provided with a releasable locking mechanism which secures the telescopic portions of the jar device from relative movement until released. The locking mechanism is released by a tensional force which ruptures one or more frangible members.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to jarring tools used in coiled tubing operations.

2. Description of the Related Art

Hydraulic jars are used to help jar loose or unstick an object in a wellbore. In milling operations, a jar is often incorporated into the running string above the milling bottom hole assembly. Jars are tools which generally include an inner central mandrel and an outer housing. These components are telescopically moveable with respect to each other. A spring is used to store energy within the jar device which can be released by actuation of a valve within the jar device. Bi-directional jars are capable of causing jarring impacts in two axial directions. A bi-directional jar device is described in U.S. Pat. No. 6,712,134 (“Modular Bi-Directional Hydraulic Jar with Rotating Capability”) issued to Stoetz. U.S. Pat. No. 6,712,134 is owned by the assignee of the present invention and is hereby incorporated by reference.

In conventional use, a jar device is run into a wellbore in a neutral position. Roughly half of the length of the mandrel is exposed when the jar is in its neutral position. The inventor has recognized that an exposed length of mandrel subjects the jar device to becoming hung up on obstacles within the wellbore. In addition, the inventor has recognized that jar devices occasionally inadvertently create jarring forces during run-in, which can cause undesirable damages to well components.

SUMMARY OF THE INVENTION

The present invention provides hydraulic jar devices which are releasably locked in an initial configuration to prevent inadvertent operation during run-in and which will eliminate exposed lengths of mandrel. The releasable lock feature may be incorporated into either bi-directional or single-directional jar devices. The releasable lock functions to isolate the jar actuation mechanism against inadvertent operation, or firing. The first and second telescopic portions of the jar device are releasably secured against axial movement with respect to each other by a releasable locking mechanism. In preferred embodiments, a mandrel sleeve radially surrounds the exposed mandrel portion of the jar device. The mandrel sleeve is also affixed to each of the first and second telescopic portions of the jar device to preclude axial movement of the first and second portions.

At least one of the first and second telescopic portions of the jar device is releasably secured to the mandrel sleeve. In a described embodiment, the mandrel sleeve is fixedly secured to the first telescopic portion of the jar device and releasably secured to the second telescopic portion of the jar device.

In a described embodiment, frangible members, such as shear screws, are used to secure the mandrel sleeve to the second telescopic portion until the jar device is ready to be actively used. Preferably, the jar device is secured in a fully contracted position. When it is desired to make the jar device active for use in creating and applying jarring forces, a tensional force of predetermined level, or overpull, is applied to the running string to shear the frangible members.

In an exemplary method of operation, the jar device is run into a wellbore on a work string. If the work string becomes stuck within the wellbore below the jar device, an operator will exert a pulling force upon the work string which is sufficient to release the releasable locking mechanism. Thereafter, the jar device can be operated normally to create jarring impacts within the wellbore.

BRIEF DESCRIPTION OF THE DRAWINGS

For a thorough understanding of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, wherein like reference numerals designate like or similar elements throughout the several figures of the drawings and wherein:

FIG. 1 is a side, cross-sectional view of an exemplary wellbore which contains a milling arrangement having a jar device in accordance with the present invention.

FIG. 2 is a side, partial cross-sectional view of an exemplary jar device constructed in accordance with the present invention, the jar device being in an initial run-in position.

FIG. 3 is an enlarged side, partial cross-sectional view of the releasable lock portion of the jar device.

FIG. 4 is an enlarged side, partial cross-sectional view of the releasable lock portion of the jar device with its telescoping portions released.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 depicts a wellbore 10 which has been drilled from the surface 12 down through the earth 14. A plug 16 is shown which was previously set within the wellbore 10. It is desired to remove the plug 16 by milling.

A milling arrangement, generally indicated at 18, is disposed within the wellbore 10 to remove the plug 16 by milling. The milling arrangement 18 includes a running string 20 which is preferably formed of coiled tubing of a type known in the art. A milling bottom hole assembly 22 is located at the distal end of the milling arrangement 18. The milling bottom hole assembly 22 typically includes a mud motor which rotationally drives a milling bit.

At surface 12 are located a number of devices which are used to operate the milling arrangement 18. A coiled tubing injection mechanism (not shown) of a type known in the art is used to inject the coiled tubing into the wellbore 10. Draw works are means to manipulate and pull on the coiled tubing running string 20. A fluid pump 24 is also located at the surface 12 to flow fluid through the coiled tubing running string 20 to operate the milling bottom hole assembly 22.

A jar device 26 is also incorporated within the milling arrangement 18 above the milling bottom hole assembly 18. The jar device 26 is functional to create and apply jarring impact forces to the milling bottom hole assembly 22. As a result, the jar device 26 is useful in situations where the milling bottom hole assembly 22 becomes stuck or hung up in the wellbore 10.

The jar device 26 is preferably a bi-directional jar device which is capable of generating and applying jarring forces in opposing axial directions (i.e., “firing” in opposing directions). In other words, a bi-directional jar device can both generate and apply a downward jarring force within the wellbore as well as an upward jarring force with the wellbore. Suitable bi-directional jar devices for use with this invention include the NOV TerraForce bidirectional jar. However, other jar devices may be used as well.

Although the particular jar device 26 is shown within a milling arrangement 18, it should be understood that the invention is not limited to situations wherein milling is conducted and that this situation is described for illustrative purposes only. In fact, jar devices such as jar device 26 can be used in other situations, such as fishing operations to contact and apply jarring forces to an object which has become stuck in the wellbore.

The interior workings of jar device 26 are not described in detail herein. Generally, jar devices convert the strain energy of a pulling force or a pushing force into kinetic energy as a hammer is caused to strike an anvil. Jar devices are typically self-contained in that they do not require a flow of liquid or air from surface in order to operate. It is noted that the jar actuation mechanism 27 may be the same as that described in U.S. Pat. No. 6,712,134 issued to Stoetz. However, other known jar designs might also be used, such as hydraulic devices which incorporate fluid reservoirs that are disposed annularly between the telescoping portions of the jar device. In this type of jar design, hydraulic oil passes through a small orifice to resist movement of the telescoping portions. The passage is formed within a moveable piston which isolates two annular fluid reservoirs as a pulling force is applied to the telescoping portions. Eventually, the moveable piston with orifice clears a narrow passage which allows oil to rush around it and allow the telescoping portions to contact each other to deliver a hammer blow to an anvil.

Referring now to FIGS. 2-4, it can be seen that exemplary jar device 26 generally includes a first telescopic portion 28 having an outer housing 30 and a first threaded end connection 32 in order to connect the jar device to the running string 20. The outer housing 30 encloses the jar actuation mechanism 27 for the jar device 26. A second telescopic portion 34 is disposed in a nested manner within the outer housing 30. The second telescopic portion 34 features a reduced diameter mandrel 36 and an enlarged diameter connection sub 38. The enlarged diameter connection sub portion 38 has a larger diameter than the mandrel 36 presents a second threaded end connection 40 which is shaped and sized to connect to the milling bottom hole assembly 22. It is noted that mandrel 36 slides in and out of the outer housing 30 of the first telescopic portion 28 during actuation of the jar device 26.

In an initial run-in position, which is illustrated in FIGS. 2 and 3, a releasable lock, generally indicated at 42, which secures the first and second telescopic portions 28, 34 against relative movement. This releasable lock isolates the actuation mechanism of the jar device 26 against inadvertent firing. The releasable lock 42 in the depicted embodiment includes a mandrel sleeve 44 which radially surrounds the mandrel 36. Mandrel sleeve 44 is shown in a transparent manner in FIG. 2. The mandrel sleeve 44 is secured to the first telescopic portion 28 by threaded connection 46. The enlarged diameter connection sub 38 has a reduced diameter neck portion 48. It is noted that conventional jar devices can have the neck portion 48 created by milling away material of the connection sub portion 38. Preferably, an annular locking groove 50 is formed in the neck portion 48.

One or more frangible shear members 52 are disposed through the mandrel sleeve 44 and into the locking groove 50. The one or more frangible shear members 52 are preferably shear screws which are designed to rupture at a predetermined shear force.

According to an exemplary method of operation, the milling arrangement 18 is run into the wellbore 10 to remove plug 16 by milling. If the milling bottom hole assembly 22 becomes stuck in the wellbore 10, an operator at surface 12 can unlock the jar device 26 to become active by pulling upwardly on the running string 20 with sufficient force to shear or rupture the frangible members 52. When the frangible members 52 are ruptured, the jar device 26 will be moved to the unlocked position shown in FIG. 4. In the unlocked position, the jar device 26 can be actuated normally to create jarring impacts, as needed.

It is noted that the jar device 26 could be used with any wellbore work string, including a fishing arrangement. The mandrel sleeve 44 also radially surrounds the mandrel 36 to prevent the mandrel 36 from being exposed to debris or obstructions within the wellbore 10. Preferably, the mandrel sleeve 44 will be shaped and sized to have substantially the same outer diameter as the outer housing 30 of the first telescopic portion 28 and the connection sub 38 of the second telescopic portion 34 so that there are no discontinuities in the outer surface of the jar device 26 which might cause hang ups.

Those of skill in the art will recognize that numerous modifications and changes may be made to the exemplary designs and embodiments described herein and that the invention is limited only by the claims that follow and any equivalents thereof. 

What is claimed is:
 1. A jar device for use in creating and applying jarring forces to a tubing string in a wellbore, the jar device comprising: a first telescopic portion securable to a first portion of the tubing string; a second telescopic portion which is disposed in a nested manner within the first telescopic portion and axially moveable with respect to the first telescopic portion, the second telescopic portion securable to a second portion of the tubing string; a jar actuation mechanism which governs axial movement of the first and second telescopic portions to cause creating of a jarring force; and a releasable locking mechanism which secures the first and telescopic portions against relative axial movement in a safety position until released.
 2. The jar device of claim 1 wherein the releasable locking mechanism comprises a frangible member which is ruptured by application of a predetermined level of shear force.
 3. The jar device of claim 1 wherein the second telescopic portion further comprises a reduced diameter mandrel; and the mandrel sleeve radially surrounds the mandrel to protect the mandrel from exposure to debris or obstructions within the wellbore.
 4. The jar device of claim 3 wherein: the mandrel sleeve is fixedly secured to the first telescopic portion; and the mandrel sleeve is releasably secured to the second telescopic portion.
 5. A jar device for use in creating and applying jarring forces to a tubing string in a wellbore, the jar device comprising: a first telescopic portion securable to a first portion of the tubing string; a second telescopic portion which is disposed in a nested manner within the first telescopic portion and axially moveable with respect to the first telescopic portion, the second telescopic portion securable to a second portion of the tubing string; a jar actuation mechanism which governs axial movement of the first and second telescopic portions to cause creating of a jarring force; and a releasable locking mechanism which secures the first and telescopic portions against relative axial movement in a safety position until released, the releasable locking mechanism being releasable by rupturing a frangible member.
 6. The jar device of claim 5 wherein the second telescopic portion further comprises a reduced diameter mandrel; and wherein the mandrel sleeve radially surrounds the mandrel to protect the mandrel from exposure to debris or obstructions within the wellbore.
 7. The jar device of claim 5 wherein: the mandrel sleeve is fixedly secured to the first telescopic portion; and the mandrel sleeve is releasably secured to the second telescopic portion.
 8. A method of operating a jar device having first and second telescoping portions, the method comprising the steps of: disposing the jar device within a wellbore, the jar device having a releasable locking mechanism which secures the first and second telescoping portions against relative movement; releasing the releasable locking mechanism to allow relative movement of the first and second telescopic portions; and actuating the jar device to cause jarring impacts within the wellbore.
 9. The method of claim 8 wherein the step of releasing the releasable locking mechanism further comprises rupturing a frangible member. 